org.hobsoft.symmetry.spring.SymmetryHttpMessageConverter.java Source code

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Here is the source code for org.hobsoft.symmetry.spring.SymmetryHttpMessageConverter.java

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/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.hobsoft.symmetry.spring;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

import org.hobsoft.symmetry.Reflector;
import org.hobsoft.symmetry.ReflectorException;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

/**
 * Spring HTTP message converter for UI components.
 * 
 * @param <T>
 *            the base component type
 */
public class SymmetryHttpMessageConverter<T> extends AbstractHttpMessageConverter<T> {
    // ----------------------------------------------------------------------------------------------------------------
    // constants
    // ----------------------------------------------------------------------------------------------------------------

    private static final Charset DEFAULT_CHARSET = StandardCharsets.ISO_8859_1;

    // ----------------------------------------------------------------------------------------------------------------
    // fields
    // ----------------------------------------------------------------------------------------------------------------

    private final Reflector<T> reflector;

    // ----------------------------------------------------------------------------------------------------------------
    // constructors
    // ----------------------------------------------------------------------------------------------------------------

    public SymmetryHttpMessageConverter(Reflector<T> reflector) {
        super(MediaType.parseMediaType(reflector.getContentType()));

        this.reflector = reflector;
    }

    // ----------------------------------------------------------------------------------------------------------------
    // HttpMessageConverter methods
    // ----------------------------------------------------------------------------------------------------------------

    @Override
    public boolean canRead(Class<?> clazz, MediaType mediaType) {
        return false;
    }

    // ----------------------------------------------------------------------------------------------------------------
    // AbstractHttpMessageConverter methods
    // ----------------------------------------------------------------------------------------------------------------

    @Override
    protected boolean supports(Class<?> clazz) {
        return reflector.getComponentType().isAssignableFrom(clazz);
    }

    @Override
    protected T readInternal(Class<? extends T> clazz, HttpInputMessage inputMessage) throws IOException {
        throw new HttpMessageNotReadableException("SymmetryHttpMessageConverter cannot read components");
    }

    @Override
    protected void writeInternal(T component, HttpOutputMessage outputMessage) throws IOException {
        OutputStream bodyStream = outputMessage.getBody();
        Charset charset = getCharset(outputMessage);
        Writer bodyWriter = new OutputStreamWriter(bodyStream, charset);

        try {
            reflector.reflect(component, bodyWriter);
        } catch (ReflectorException exception) {
            throw new HttpMessageNotWritableException("Error writing component", exception);
        }

        bodyWriter.flush();
    }

    // ----------------------------------------------------------------------------------------------------------------
    // private methods
    // ----------------------------------------------------------------------------------------------------------------

    private static Charset getCharset(HttpOutputMessage outputMessage) {
        Charset charset = outputMessage.getHeaders().getContentType().getCharSet();

        if (charset == null) {
            charset = DEFAULT_CHARSET;
        }

        return charset;
    }
}